US3636477A - Frequency modulator including selectively controllable delay line - Google Patents

Frequency modulator including selectively controllable delay line Download PDF

Info

Publication number
US3636477A
US3636477A US874294A US3636477DA US3636477A US 3636477 A US3636477 A US 3636477A US 874294 A US874294 A US 874294A US 3636477D A US3636477D A US 3636477DA US 3636477 A US3636477 A US 3636477A
Authority
US
United States
Prior art keywords
frequency
carrier
modulator
preselected
amplifier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US874294A
Inventor
Jacques Selz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel CIT SA
Nokia Inc
Original Assignee
Nokia Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Inc filed Critical Nokia Inc
Application granted granted Critical
Publication of US3636477A publication Critical patent/US3636477A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/081—Details of the phase-locked loop provided with an additional controlled phase shifter
    • H03L7/0812—Details of the phase-locked loop provided with an additional controlled phase shifter and where no voltage or current controlled oscillator is used
    • H03L7/0814—Details of the phase-locked loop provided with an additional controlled phase shifter and where no voltage or current controlled oscillator is used the phase shifting device being digitally controlled

Definitions

  • ABSTRACT A frequency modulated HF wave is obtained by applying a HF carrier wave of preselected frequency to a variable phase shifter consisting of a delay line made up of a plurality of switchable delay units controlled by a pulse counter to effect a periodic phase shift of 360, wide band operation being ensured by correction of the effective capacity of the counter depending on the value of high frequency selected.
  • the invention concerns a device providing frequency modulation of a carrier wave whose frequency can be selected within a wide band.
  • the resulting frequency For a phase rotation produced N times per second in a particular direction, the resulting frequency has the value F -l-N; if produced in the other direction, the resulting frequency has the value l -N.
  • a transposed frequency For any fixed value of N there is obtained a transposed frequency; for a value of N varying in accordance with an external signal, a wave with a carrier frequency F, is obtained, frequency-modulated by the external signal.
  • this principle for a fairly high carrier frequency such as some tens or hundreds of megahertz, proceeds as follows:
  • the fixed-frequency wave F is applied to a delay line consisting of a series of binary-switched cells forming in all n dephasing steps.
  • a primary frequency modulator is used working at a comparatively low carrier frequency 1",, (some hundreds of kHz. or MHz.) to which the modulating signal to be transmitted is'applied; this resulting modulated frequency has the value #1, M
  • Such a device functions correctly only at one particular value of the high-frequency carrier wave.
  • the present invention provides for this problem a sufficiently accurate approximation for practical use.
  • a modulator for frequency modulation of a relatively high carrier-frequency variable over a relatively wide range includes: an auxiliary modulator arranged to receive the modulation frequency and adapted to modulate a relatively low auxiliary carrier-frequency; a counter connected to count successive cycles of the modulated auxiliary carrier-frequency; logic circuitry arranged to sense a preselected carrier-frequency and adapted to maintain in the counter a fixed minimum reference value corresponding to the preselected carrier-frequency; and a chain of delay elements arranged to receive the carrier-frequency and adapted to be switched sequentially by preselected states of the counter to maintain a phase rotation of the order of 360.
  • FIG. 1 a block diagram of a modulator in which the operation of the counter is controlled by an element applying tivibrator frequency modulators with high-frequency stability are well known in the art.
  • the primary modulator l 1 receives from signals from a generator 12, such as a microphone, through a variable-gain amplifier 13.
  • a counter 15 receives at its input the frequency supplied by the primary frequency modulator l1, and advances one step for each period of the modulated frequency f received.
  • the counter 15 is a binary counter with five stages.
  • a high-frequency generator 19 supplying a preselected carrier-frequency F is connected with the input of a delay line 17 comprising five cells, marked 1, 2, Vietnamese, 5, which can be individually short circuited or activated by circuit breakers a, b, c, d, e, respectively.
  • the circuit breakers a-e are shown as mechanical units to simplify the diagram, but are in practice of a quick-acting electronic type such as diodes.
  • a decoder 16 in accordance with various preselected states of the counter 15, supplies opening or closing orders to the switching elements a-e.
  • the output terminal 18 receives a high-frequency, modulated wave.
  • the high-frequency generator 19 consists of a frequency synthesizer whose output frequency is controlled by a digital control element 20 in which the preselected frequency value F is set directly by decimal indexes.
  • a digital-analog converter 21 receives the digital states of the element 20 at its input, and supplies gain control signals to the amplifier 13.
  • the mode of operation is as follows:
  • the counter 15 has a capacity of 32.
  • a phase rotation of 360 is supplied by the 32 states of the counter 15 switching the delay line 17.
  • the upper limit of the range corresponds to a phase rotation of 720.
  • the reference value only 16 operations of the delay line 17 are used, for which purpose the logic element 14 applies to the counter 15 of a fixed reference value 16.
  • the counter passes from 16 to 32, returns to 16, moves again to 32 and continues to cycle between 16 and 32.
  • the phase-error d over the phase circle will be 22.5" at the peak of the range. This can be reduced by half in absolute value if the corrections R are applied, not to the reference values F, but midway between the intervals: in such conditions, there is obtained on either side of the correction frequency Le, a maximum error of the order of 10 at the top of the range.
  • the index of the frequency modulation will increase, since the frequency vector rotates more rapidly over the phase circle, due to the fact that there are fewer steps involved in passing round the circle. If the original maximum frequency excursion is to be retained the intensity of the modulating signal must be reduced. It is for this reason that the gain of the amplifier 13 is variable in accordance with the frequency set in the controller 20.
  • the frequency of the generator 19 is controlled, manually for example, by an element 22.
  • the output frequency of the generator 19 is received by the delay line 17, as before, and is further applied to a discrimina tor 23 whose output signal is applied to the gain control of the amplifier l3, and on the other hand to the component 14 through an analogue-digital converter 24.
  • control signal is provided by the output voltage of the frequency discriminator.
  • a modulator for frequency modulation of a relatively high carrier-frequency variable over a relatively wide range comprising: modulator means responsive to a modulation frequency for modulating a relatively low auxiliary carrierfrequency with said modulation frequency; a counter connected to count successive cycles of the modulated auxiliary carrier-frequency; logic circuit means responsive to a signal representing a preselected value of said high carrier-frequency for applying to said counter a fixed minimum reference value corresponding to the preselected carrier-frequency; variable means for generating said preselected high carrier-frequency; a chain of delay elements connected to receive said preselected carrier-frequency and means for switching said delay elements sequentially in accordance with the changing states of said counter to maintain a phase rotation of the order 2.
  • a modulator as claimed in claim 2 including circuitry for providing the preselected value of carrier-frequency and a frequency discriminator connected to sense the carrierfrequency, said logic circuit means being connected to the frequency discriminator via an analogue-to-digital converter to sense the carrier frequency.
  • a modulator as claimed in claim 1 including a digital element for indicating said preselected carrier-frequency and generator means connected to said digital element for supplying said preselected carrier-frequency to said chain of delay elements.
  • a modulator as claimed in claim 5 in which said amplifier is connected to said digital element to sense the preselected value of the carrier-frequency via an analogue-to-digital converter.

Landscapes

  • Transmitters (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Networks Using Active Elements (AREA)

Abstract

A frequency modulated HF wave is obtained by applying a HF carrier wave of preselected frequency to a variable phase shifter consisting of a delay line made up of a plurality of switchable delay units controlled by a pulse counter to effect a periodic phase shift of 360*, wide band operation being ensured by correction of the effective capacity of the counter depending on the value of high frequency selected.

Description

United States Patent Selz [4 1 Jan. 18, 1972 [54] FREQUENCY MODULATOR INCLUDING SELECTIVELY CONTROLLABLE DELAY LINE Inventor: Jacques Selz, Viroflay, France Assignee: c. i. T. Compagnie Industrielle Des Telecommunications, Paris, France Filed: Nov. 5, 1969 Appl. No.: 874,294
Foreign Application Priority Data I 332/9, 9 T; 328/55, 155, 134; 325/38, 38 A, 38 B, 163, 148; 307/295 FREQUENCY MODULATOR [56] References Cited UNITED STATES PATENTS 3,097,338 7/1963 Pinet et al ..325/38 3,271,688 9/1966 Gschwind et al. ..328/55 3,278,907 10/1966 Barry et a1. ..307/295 X 3,312,903 4/1967 Webb ..332/18 X 3,421,088 1/1969 Salley et al.. ....332/l6 X 3,478,170 11/1969 Hanni ..332/9 Primary Examiner-Alfred L. Brody Attorney-Craig, Antonelli & Hill [57] ABSTRACT A frequency modulated HF wave is obtained by applying a HF carrier wave of preselected frequency to a variable phase shifter consisting of a delay line made up of a plurality of switchable delay units controlled by a pulse counter to effect a periodic phase shift of 360, wide band operation being ensured by correction of the effective capacity of the counter depending on the value of high frequency selected.
DIGITAL CONTROL ELEMENT osc.
9 Claims, 2 Drawing Figures LOGIC CIRCUIT COUNTER ,DECODER Va b c d e 17 I DELAY LINE PmENNnJNwmz 335363171 FIG I LOGIC j CIRCUIT 15 FREQUENCY "I MODULATOR DIGITAL m, CONTROL 2O DE D f16 ELEMENT [Ma r r I r 'osc. 4 7
DELAY LINE 18 F IG .2
are 1N? 1/14 CONVERTER EREouENcY MODULATOR w 16 DISC. DECODER 22 19 a b} c) d} e) 17 0167 W CONTROL 050. E E El [-1 ELEMENT DELAY LINE 18 FREQUENCY MODULATOR INCLUDING SELECTYVELY CONTROLLABLE DELAY LINE The invention concerns a device providing frequency modulation of a carrier wave whose frequency can be selected within a wide band.
The fundamental principle applied in this invention consists in rotating the phase of a fixed frequency carrier wave F generally defined by quantized stages B, such that B=360/n, the phase successively assuming the value:0,
B, 2 B,...(nl) ,8, n/3=360, [3, etc.
For a phase rotation produced N times per second in a particular direction, the resulting frequency has the value F -l-N; if produced in the other direction, the resulting frequency has the value l -N. For any fixed value of N there is obtained a transposed frequency; for a value of N varying in accordance with an external signal, a wave with a carrier frequency F, is obtained, frequency-modulated by the external signal.
As an example, this principle, for a fairly high carrier frequency such as some tens or hundreds of megahertz, proceeds as follows:
1. The fixed-frequency wave F is applied to a delay line consisting of a series of binary-switched cells forming in all n dephasing steps.
2. A primary frequency modulator is used working at a comparatively low carrier frequency 1",, (some hundreds of kHz. or MHz.) to which the modulating signal to be transmitted is'applied; this resulting modulated frequency has the value #1, M
3. The switching of the n dephasing cells in binary series is controlled by the above frequency: Ff ztAfi The result is a high-frequency wave modulated in the frequency:
F =F,,+(f,tAfln). By this means, a high-frequency modulated wave is obtained with a highly stable carrier frequency, as well as high purity.
Such a device, however, functions correctly only at one particular value of the high-frequency carrier wave.
In fact, if we assume a delay line with n steps each introducing a delay T, at a fixed frequency F, the delay Twill produce a phase shift of B=(360/n; after n switching steps, the phase angle will be 0", but, for any other high-frequency F, the unit delay time T will give a phase shift of B'=(360/n) (F/F,,). After it switching steps, the phase will not have rotated through 360(=o); consequently, when the (n+1) th switching step takes place, instead ofa phase shift B equal to the preceding steps, we get a different phase-shift value.
The present invention provides for this problem a sufficiently accurate approximation for practical use.
According to the invention, a modulator for frequency modulation of a relatively high carrier-frequency variable over a relatively wide range, includes: an auxiliary modulator arranged to receive the modulation frequency and adapted to modulate a relatively low auxiliary carrier-frequency; a counter connected to count successive cycles of the modulated auxiliary carrier-frequency; logic circuitry arranged to sense a preselected carrier-frequency and adapted to maintain in the counter a fixed minimum reference value corresponding to the preselected carrier-frequency; and a chain of delay elements arranged to receive the carrier-frequency and adapted to be switched sequentially by preselected states of the counter to maintain a phase rotation of the order of 360.
The invention will now be described in more detail by way of examples, with reference to the accompanying drawing, showing:
in FIG. 1 a block diagram of a modulator in which the operation of the counter is controlled by an element applying tivibrator frequency modulators with high-frequency stability are well known in the art. The primary modulator l 1 receives from signals from a generator 12, such as a microphone, through a variable-gain amplifier 13.
A counter 15 receives at its input the frequency supplied by the primary frequency modulator l1, and advances one step for each period of the modulated frequency f received. The counter 15 is a binary counter with five stages.
A high-frequency generator 19 supplying a preselected carrier-frequency F is connected with the input of a delay line 17 comprising five cells, marked 1, 2,....., 5, which can be individually short circuited or activated by circuit breakers a, b, c, d, e, respectively. The circuit breakers a-e are shown as mechanical units to simplify the diagram, but are in practice of a quick-acting electronic type such as diodes.
A decoder 16, in accordance with various preselected states of the counter 15, supplies opening or closing orders to the switching elements a-e. The output terminal 18 receives a high-frequency, modulated wave.
The high-frequency generator 19 consists of a frequency synthesizer whose output frequency is controlled by a digital control element 20 in which the preselected frequency value F is set directly by decimal indexes. A logic element 14, receiving the digital states of the controller 20, supplies the counter 15 with a preselected fixed minimum reference value differing from zero, and depending on a preselected one of the frequency values held in a memory incorporated in the element 14.
A digital-analog converter 21 receives the digital states of the element 20 at its input, and supplies gain control signals to the amplifier 13.
The mode of operation is as follows:
If the carrier-frequency band to be covered is one octave, the counter 15 has a capacity of 32. For a first frequency F, forming the lower limit of the range, a phase rotation of 360 is supplied by the 32 states of the counter 15 switching the delay line 17.
In this case, the upper limit of the range corresponds to a phase rotation of 720. To reduce this to 360, the reference value, only 16 operations of the delay line 17 are used, for which purpose the logic element 14 applies to the counter 15 of a fixed reference value 16. Thus, the counter passes from 16 to 32, returns to 16, moves again to 32 and continues to cycle between 16 and 32.
For intermediate values between and 320 MHz., the corrections applied to counter 15 at indicated reference frequencies, are applied according to anexpression n-F the counter capacity, as shown in the following table:
In this table, F is a reference frequency at which the content of the counter 15 is changed by one unit; n is the capacity or effective capacity of the counter 15; R is the reference value applied continuously to the counter by the logic unit 14.
With an arrangement as above, the phase-error d over the phase circle will be 22.5" at the peak of the range. This can be reduced by half in absolute value if the corrections R are applied, not to the reference values F, but midway between the intervals: in such conditions, there is obtained on either side of the correction frequency Le, a maximum error of the order of 10 at the top of the range.
Obviously, this error will be diminished if the total number of phase steps is increased.
With such an arrangement, when the high frequency F increases, other things beingequal, the index of the frequency modulation will increase, since the frequency vector rotates more rapidly over the phase circle, due to the fact that there are fewer steps involved in passing round the circle. If the original maximum frequency excursion is to be retained the intensity of the modulating signal must be reduced. It is for this reason that the gain of the amplifier 13 is variable in accordance with the frequency set in the controller 20.
In FIG. 2, where references common to FIG. 1 have the same significance as in the latter figure, the frequency of the generator 19 is controlled, manually for example, by an element 22. The output frequency of the generator 19 is received by the delay line 17, as before, and is further applied to a discrimina tor 23 whose output signal is applied to the gain control of the amplifier l3, and on the other hand to the component 14 through an analogue-digital converter 24.
The operation is the same as in the case of FIG. 1; the only difference is that the control signal is provided by the output voltage of the frequency discriminator.
What we claim is:
l. A modulator for frequency modulation of a relatively high carrier-frequency variable over a relatively wide range, comprising: modulator means responsive to a modulation frequency for modulating a relatively low auxiliary carrierfrequency with said modulation frequency; a counter connected to count successive cycles of the modulated auxiliary carrier-frequency; logic circuit means responsive to a signal representing a preselected value of said high carrier-frequency for applying to said counter a fixed minimum reference value corresponding to the preselected carrier-frequency; variable means for generating said preselected high carrier-frequency; a chain of delay elements connected to receive said preselected carrier-frequency and means for switching said delay elements sequentially in accordance with the changing states of said counter to maintain a phase rotation of the order 2. A modulator as claimed in claim 1, including an amplifier connected to said modulator means for supplying said modulation frequency thereto, the gain of said amplifier being controlled in accordance with said signal representing said preselected value of said carrier-frequency.
3. A modulator as claimed in claim 2, including circuitry for providing the preselected value of carrier-frequency and a frequency discriminator connected to sense the carrierfrequency, said logic circuit means being connected to the frequency discriminator via an analogue-to-digital converter to sense the carrier frequency.
4. A modulator as claimed in claim 1, including a digital element for indicating said preselected carrier-frequency and generator means connected to said digital element for supplying said preselected carrier-frequency to said chain of delay elements.
5. A modulator as claimed in claim 4, in which the logic circuit means is connected to said digital element to sense said preselected value of carrier-frequency.
6. A modulator as claimed in claim 5, including an amplifier connected to said modulator means for supplying said modulation frequency thereto, the gain of said amplifier being controlled in accordance with said signal representing said preselected value of said carrier-frequency.
7. A modulator as claimed in claim 6, in which said amplificr is connected to said digital element to sense the preselected carrier-frequency via an analogue-to-digital converter.
8. A modulator as claimed in claim 1 in which the logic circuitry includes a memory for holding correction frequencies of the carrier-frequency band.
9. A modulator as claimed in claim 5 in which said amplifier is connected to said digital element to sense the preselected value of the carrier-frequency via an analogue-to-digital converter.

Claims (9)

1. A modulator for frequency modulation of a relatively high carrier-frequency variable over a relatively wide range, comprising: modulator means responsive to a modulation frequency for modulating a relatively low auxiliary carrier-frequency with said modulation frequency; a counter connected to count successive cycles of the modulated auxiliary carrier-frequency; logic circuit means responsive to a signal representing a preselected value of said high carrier-frequency for applying to said counter a fixed minimum reference value corresponding to the preselected carrier-frequency; variable means for generating said preselected high carrier-frequency; a chain of delay elements connected to receive said preselected carrier-frequency and means for switching said delay elements sequentially in accordance with the changing states of said counter to maintain a phase rotation of the order of 360*.
2. A modulator as claimed in claim 1, including an amplifier connected to said modulator means for supplying said modulation frequency thereto, the gain of said ampLifier being controlled in accordance with said signal representing said preselected value of said carrier-frequency.
3. A modulator as claimed in claim 2, including circuitry for providing the preselected value of carrier-frequency and a frequency discriminator connected to sense the carrier-frequency, said logic circuit means being connected to the frequency discriminator via an analogue-to-digital converter to sense the carrier frequency.
4. A modulator as claimed in claim 1, including a digital element for indicating said preselected carrier-frequency and generator means connected to said digital element for supplying said preselected carrier-frequency to said chain of delay elements.
5. A modulator as claimed in claim 4, in which the logic circuit means is connected to said digital element to sense said preselected value of carrier-frequency.
6. A modulator as claimed in claim 5, including an amplifier connected to said modulator means for supplying said modulation frequency thereto, the gain of said amplifier being controlled in accordance with said signal representing said preselected value of said carrier-frequency.
7. A modulator as claimed in claim 6, in which said amplifier is connected to said digital element to sense the preselected carrier-frequency via an analogue-to-digital converter.
8. A modulator as claimed in claim 1 in which the logic circuitry includes a memory for holding correction frequencies of the carrier-frequency band.
9. A modulator as claimed in claim 5 in which said amplifier is connected to said digital element to sense the preselected value of the carrier-frequency via an analogue-to-digital converter.
US874294A 1968-11-05 1969-11-05 Frequency modulator including selectively controllable delay line Expired - Lifetime US3636477A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR172628 1968-11-05
FR174264 1968-11-18

Publications (1)

Publication Number Publication Date
US3636477A true US3636477A (en) 1972-01-18

Family

ID=26182299

Family Applications (1)

Application Number Title Priority Date Filing Date
US874294A Expired - Lifetime US3636477A (en) 1968-11-05 1969-11-05 Frequency modulator including selectively controllable delay line

Country Status (6)

Country Link
US (1) US3636477A (en)
BE (1) BE740815A (en)
DE (1) DE1955708A1 (en)
FR (1) FR96107E (en)
GB (1) GB1244686A (en)
NL (1) NL6916059A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3740669A (en) * 1971-11-01 1973-06-19 Rca Corp M-ary fsk digital modulator
US3792378A (en) * 1971-09-08 1974-02-12 Us Navy Digitally controlled rf sweep generator
US3824498A (en) * 1972-12-22 1974-07-16 Dallas Instr Inc Digital processor for selectively synthesizing sinusoidal waveforms and frequency modulations
US4266197A (en) * 1977-05-30 1981-05-05 Rca Corporation Remote control TV subcarrier phase shifter system
US4649553A (en) * 1985-03-26 1987-03-10 Madni Asad M Microwave digital phase-shifter apparatus and method for construction
US5016259A (en) * 1989-03-03 1991-05-14 The Grass Valley Group, Inc. Low jitter DDFS FSK modulator
US5111206A (en) * 1983-09-22 1992-05-05 Systron Donner Corp. Velocity deception apparatus
US20090304053A1 (en) * 2008-06-10 2009-12-10 Advantest Corporation Digital modulator, digital modulating method, digital transceiver system, and testing apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE202013103960U1 (en) 2013-09-03 2013-10-08 Umfotec Gmbh resonator

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3792378A (en) * 1971-09-08 1974-02-12 Us Navy Digitally controlled rf sweep generator
US3740669A (en) * 1971-11-01 1973-06-19 Rca Corp M-ary fsk digital modulator
US3824498A (en) * 1972-12-22 1974-07-16 Dallas Instr Inc Digital processor for selectively synthesizing sinusoidal waveforms and frequency modulations
US4266197A (en) * 1977-05-30 1981-05-05 Rca Corporation Remote control TV subcarrier phase shifter system
US5111206A (en) * 1983-09-22 1992-05-05 Systron Donner Corp. Velocity deception apparatus
US4649553A (en) * 1985-03-26 1987-03-10 Madni Asad M Microwave digital phase-shifter apparatus and method for construction
US5016259A (en) * 1989-03-03 1991-05-14 The Grass Valley Group, Inc. Low jitter DDFS FSK modulator
US20090304053A1 (en) * 2008-06-10 2009-12-10 Advantest Corporation Digital modulator, digital modulating method, digital transceiver system, and testing apparatus
US8014465B2 (en) * 2008-06-10 2011-09-06 Advantest Corporation Digital modulator, digital modulating method, digital transceiver system, and testing apparatus

Also Published As

Publication number Publication date
FR96107E (en) 1972-05-19
DE1955708A1 (en) 1970-05-06
BE740815A (en) 1970-04-27
NL6916059A (en) 1970-05-08
GB1244686A (en) 1971-09-02

Similar Documents

Publication Publication Date Title
US3641442A (en) Digital frequency synthesizer
US4320361A (en) Amplitude and frequency modulators using a switchable component controlled by data signals
US3548342A (en) Digitally controlled amplitude modulation circuit
US5495206A (en) Fractional N frequency synthesis with residual error correction and method thereof
US4965531A (en) Frequency synthesizers having dividing ratio controlled by sigma-delta modulator
US4103250A (en) Fast frequency hopping synthesizer
GB859002A (en) Improvements in or relating to phase modulators for carrier communication systems
US3636477A (en) Frequency modulator including selectively controllable delay line
US4206425A (en) Digitized frequency synthesizer
US4331941A (en) Digital phase domain amplitude modulation method and apparatus
GB2214012A (en) Frequency or phase modulation
US5053728A (en) Phase locked loop frequency modulator using data modulated digital synthesizer as reference
US3997855A (en) Digital FSK time rate of change modulator
CA1238365A (en) Device for generating a frequency modulated signal
US3932704A (en) Coherent digital frequency shift keying system
US4210879A (en) Four-phase staggered shift keying modulator system
US3555458A (en) Side band generator
US5014285A (en) Frequency shift keying communication system with selectable carrier frequencies
US3740669A (en) M-ary fsk digital modulator
GB1575629A (en) Generator for generating sinusoidal electrical signals which are phase or frequency modulated by a digital method
US3902013A (en) Frequency synthesis control for a frequency-modulated telegraphic transmitter
SU1035776A1 (en) Digital frequency synthesizer with frequency modulation
GB1589636A (en) Signal generator
JPS61172464A (en) Modulation circuit
SU1202015A1 (en) Generator of linear-frequency-modulated signals